Embodiments relate to an imaging system and, more particularly, to a system and method to optically detect a latent print or contaminant upon a surface.
A latent print may be an invisible fingerprint impression, footprint impression, or palm print impression left on a surface following surface contact caused by the perspiration on ridges of an individual's skin coming in contact with the surface and leaving perspiration behind, making an invisible impression on the surface as a result. Perspiration is known to contain water, salt, amino acids, and oils, which allow impressions to be made. The natural oils of the body preserve the print, where the impression left is utterly distinct so that no two humans have the same latent print. Though discussed as being invisible above, the latent print may also be partially visible. Also, the latent print may be made of non-bodily fluids or particles.
Conventional methods for extracting fingerprints usually involve adding chemicals or powders to the print. Such conventional methods can present an immediate dilemma in that they force the investigator to make a decision as to whether to dust for prints versus swabbing for DNA evidence. Either approach results in destroying, or removing, the prints as they are originally found since the prints are no longer on their original surface.
Automatic non-contact latent fingerprint detection systems are also known that avoid the need to add chemicals or powders that can disturb the surface chemicals of the fingerprint. Such systems generally include a single light source, utilize only diffuse reflectance ((reject specular reflection (glare)), and are generally limited to fingerprinting the area of one's finger, or an area about that size. However, systems using specular reflection are also known, though they are believed to be limited. Furthermore, optically lifting a latent print occurs with an imaging system, and usually also the light emitting device, located a few inches, such as, but not limited to, about 6 inches (approximately 15 centimeters) to about 24 inches (approximately 61 centimeters) from a surface where a latent print is expected to exist. Such distances between the imaging device and surface are used because optical detection is usually critically dependent on image contrast and high resolution. Latent prints are very low contrast objects and therefore using only existing optical techniques when the print is on a rough surface is not practical. Optically lifting a finger print from longer distances has not proven to be possible since sufficient resolution and sensitivity as is obtained at the closer distance has not be realized previously. Furthermore, since latent prints are usually not visible to a human eye, depending on a size of an area to search for latent prints, chances of failing to locate and acquire all latent prints are possible.
Entities desiring to detect latent prints at a longer distance would benefit from a system and method where a latent print may be optically detected and acquired without damaging the print while also providing resolution and sensitivity with sufficient clarity to identify an entity that made the print, especially where a map of the target area may be made, such as, but not limited to, a three dimensional map, so that any doubt about missing any latent print is resolved.